attention, shoppers, a large-scale credit carp theft is sweeping 63 stores. Barnes and noble. How did thieves get into the checkout machines. Pierre thomas has been investigating that today. Reporter: Today barnes and noble announced it has been the victim of a massive, sophisticated scheme targeting credit and debit cards. Thieves went after these tiny devices known as pin pads we routinely use to swipe our credit and debit cards for purchases. 63 stores in nine states were hit, potentially affecting thousands of customers. Each time a purchase was made the pin pad beamed the customer's private financial information to the crooks. The crooks could then withdraw money from bank accounts and make unauthorized credit purchases. I think it's really scary. I'm worried. Reporter: We went to stores today in new york and california and the pin pad devices were gone. Barnes and noble was so concerned it took the pin pads out of all its 700 stores nationwide. Tonight, it's unclear how the thieving infiltrated the stores. What is clear is the ominous potential for the thieves to run up thousands of dollars in purchases, ruin credit and even steal customer identities. They now have to monitor credit reports, they have to monitor their bank statements. Reporter: Authorities now warn they're expecting more scams like this, targeting other stores. Pierre thomas, abc news, new

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